1. Field of the Invention
The present invention relates to a hand-held electrical tool, in particular to a hand-held power tool such as screwdriving tool, drilling, chisel or combination power tool and, more specifically to a driving unit such as, e.g., a brushless motor, for such a power tool and which includes a stator located in the drive unit housing and having a longitudinal axial extent between two opposite ends of the stator, an end member provided at each of the opposite ends of the stator a rotor provided with at least one permanent magnet, arranged in a receiving space limited by the stator and the end members, and rotatably supported by a drive axle on the end members, and a fan rotatably connected with the drive axle for generating a cooling flow from one stator end to another stator end between an inner surface of the drive unit housing and an outer surface of the stator for cooling the stator and the drive unit.
2. Description of the Prior Art
In such drive units, an essentially complete encapsulation of the receiving space, which is formed by the stator and end members, prevents the metal particles which are carried by the air flow from reaching the receiving space and accumulating on the permanent magnet(s) in a damaging amount. The cooling of the motor is effected simply by a cooling flow along the stator outer surface along a predetermined path.
A drive unit of the type described above is disclosed in British Publication GB 2,293,282A. It discloses a brushless motor in which the rotor is completely encapsulated by stator and end plates which surround the rotor from all sides. On the outer side of one of the end plates remote from the stator, there is provided a fan that produces an air flow along the outer surface of the stator. Here, the end plates form, together with the stator, a common outer surface in which a plurality of elongate slots is formed. The slots form a plurality of cooling ribs extending along the length of the arrangement and projecting from the cover plates and the stator.
The drawback of the drive unit described above consists in that the cooling effect of the produced cooling flow is relatively small, which results in that either the power of the drive unit must be kept low or a relatively more powerful fan must be used.
Accordingly, an object of the present invention is to provide a drive unit in which the above-described drawback(s) is (are) eliminated and a better cooling effect is achieved.